How to build a GPS receiver?

[ihavenoname]

I'm a high school student working on an anti-theft project and I kind of think I'm in way over my head. Maybe if someone could help explain a couple things for me since I'm having trouble find it on the internet. I want to build a small GPS receiver into portable electronice devices. If that's the case, (let's say that that electronic device got stolen) would I be able to track it through a some sort of program on my PC/notebook or through a website or something. Where can I buy the components to build the GPS receiver and how much would it cost me? What programs would I have to have for this to work?

If it helps, I already know much about programming. i know C++ and JAVA, and I know how to create a website and about webpage/website design.

It would be great if you could site a source too.

Thanks!!!

 

[dknguyen]

You are never going to be able to "build" a GPS receiver on your own. Buy a GPS OEM module and integrate it into the rest of your system. For example, like one off of www.sparkfun.com.

SparkFun Electronics
SparkFun Electronics

It may or may not have occured to you that the hard part is not receiving the GPS signal and generating the data for your current position, but a way to get this positional data back to you when your things has been stolen! Then you need some other kind of transmitter of something. The easiest, longest range way is probably not an standalone wireless transmitter like an RF modem, but a cellular modem that can use infrastructure to extend it's range so you can actually get the positional data of your stolen item back to you when it is many km away from you. Costs money though, but if you have a cell-phone with a SMS card, you can do it more cheaply by dialing into the tracking module only when you need to and having it spit back data for a short period of time and then hanging up.

 

[abel2b]

I did a similar search a while back you have to mostly decide how to retransmit the data back your pc or receiver, usually the GPS antenna Byonics - TinyTrak - GPS Receivers does al the math onboard and spits out the the data you need in either RS-232 or usb, depending on the hardware you buy, that it´s compatible with most gps software. Checkout Byonics - their tinytrack transmit over radio gprs format. then there is gsm modem also.

 

[Ubergeek63]

I checked out Spark thinking maybe I was missing something, I was wrong... the best the had was about $60 for a module.

If you want to do it yourself go to Mouser for $30:

V23993-A1037-A

Or take a look at **broken link removed**

 

[Stellarcore]

I used the EM-408 from sparkfun for a university project. Great little device; easy to use and surprisingly accurate.

However, you'll probably end up spending more than just the $60 after all the extras are bought. In my case I also bought a bunch of the surface mount connectors, and the magnetic external antennae, and the pigtail that converts the external antennae connector from mini-ccx to ccx. After buying three modules with all the extras and shipping, it worked out to be about $100 per unit.

 

[Ubergeek63]

if you want to be cheap:

**broken link removed**

or instead of the $50 antenna the store would have you buy:

**broken link removed**

 

[Oznog]

Right, you can't build a module. It requires an incredible degree of complexity and accuracy.
Actually I got some precision modules off a guy on Ebay, about $40 w/antenna.

So what you need is a Simple Messaging System (SMS) module which can tx/rx data from the cell phone system. Unfortunately there's not many other ways to do long-range communication from miles away. The SMS will cost you. I don't know much about using them. Well, you say it's a school project and if you wanna do something unrealistic like a transmitter that only goes 50 ft, well I won't tell on you.

Now the GPS module will output NMEA data- all modules do. That's conveyed as serial data, 8N1 4800 or 9600 baud. This may be a 3.3V or 5v signal level and your PC may or may not read that without a transceiver chip. Some modules have a USB interface, and will still format the data as NMEA sentences, but over the USB interface.

Anyhow what you need is a microcontroller- such as a PIC- to recognize a query from the SMS module and power up the GPS and message back a location and potentially a speed and direction.

 

[Yongleloo]

I used the EM-408 from sparkfun for a university project. Great little device; easy to use and surprisingly accurate.

However, you'll probably end up spending more than just the $60 after all the extras are bought. In my case I also bought a bunch of the surface mount connectors, and the magnetic external antennae, and the pigtail that converts the external antennae connector from mini-ccx to ccx. After buying three modules with all the extras and shipping, it worked out to be about $100 per unit.

Do you have any source code or examples I can peruse? I just brought one recently

 

[Super_voip]

I built my own GPS antenna based (1999) on the Adventures in GPS antenna construction version, before the MMIC was included. I, however, did include a MMIC located under the board to reduce the possibility of feedback. Works well, but with the price of ready made GPS antennas so low I wouldn't bother these days.

 

[Stellarcore]

The modules are really quite simple. You can connect the EM-408 directly to a MAX232 and then to your computer if you want to just play with the raw data. One thing to be aware of though, is that the EM408 has a 3.3 volt output. To get around this, you can use a low voltage PIC at a comparable voltage or you can setup some kind of buffer between them.

From there, you need can communicate using the NMEA or Sirf Binary protocols. If you want, you dont even need to send anything to the module and just listen to the stream of messages it sends continuously. In my project, I sent a few commands to the EM-408 so that I could disable all messages so that I could just poll for the data when I needed.

Here is the NMEA Protocol Reference Manual:
https://www.electro-tech-online.com/custompdfs/2008/06/NMEA20Reference20Manual1.pdf